Tuesday, November 7, 2017

[Ichthyology • 2017] A Revision of Paracanthocobitis zonalternans (Cypriniformes: Nemacheilidae) Species Complex with Descriptions of Three New Species


FIGURE 4. Paracanthocobitis zonalternans from the Salween drainage, Thailand.
 UF 188197, Mae Hong Son Province, live

 photo by Z. S. Randall (UF).

Abstract

The Paracanthocobitis zonalternans species complex is revised based on analysis of morphological and molecular data. Three new speciesP. nigrolineataP. marmorata, and P. triangula are described, and P. phuketensis is removed from synonymy. All species are described morphologically, geographic ranges are delimited, and relationships are discussed for those for which molecular data (cytochrome c oxidase subunit 1 - COI) are available. In view of the morphological similarities of some of the species, a surprising result of this study was the moderately large genetic distances among species. Uncorrected COI p-distances between geographic clades of P. zonalternans ranged from 7.6–9.3%, suggesting that the species are reproductively isolated from one another even though morphological changes are minor. Paracanthocobitis phuketensis, distributed in several rivers draining to the Gulf of Thailand and to the Andaman Sea, shows considerable intraspecific variation that should be explored in detail for historical and ecological explanations. Cobitis chlorosoma McClelland, 1839 from Assam, India, is a synonym of P. botia, not P. zonalternans.

Keywords:  Pisces, Cypriniformes, Southeast Asia, zipper loaches, Acanthocobitis



Paracanthocobitis zonalternans (Blyth, 1860) 
Dwarf Zipper Loach

Cobitis zonalternans Blyth, 1860:172. Type locality: Tenasserim provinces, Burma. Two syntypes (Day, 1869:551; Day, 1872:186), presumed lost (Hora, 1929:319). Neotype, ZSM 27468, designated by Kottelat, 1990:42, Huai Mae Charno, 4 km south Amphoe Mae Ramat on road 1085 [approximately 16.967N, 98.567E], Tak Province, Salween drainage, Thailand. 
Nemacheilus zonalternans.—Day, 1869:551. 
Nemachilus zonalternans.—Day, 1889:232. 
Noemacheilus zonalternans.—Sen, 1985:119, fig. 63. 
Acanthocobitis zonalternans.—Kottelat, 1990:13. 
Acanthocobitis (Paracanthocobitis) zonalternans.—Grant, 2007:3.
  Paracanthocobitis zonalternans.—Singer & Page, 2015:396.

Diagnosis. Paracanthocobitis zonalternans is distinguished from all other species of Paracanthocobitis by combination of incomplete lateral line ending near dorsal-fin insertion; 9½–10½ branched dorsal-fin rays; axillary pelvic lobe present; series of black blotches, usually without black stripe but with faint dusky stripe, along side of body, usually ending near dorsal-fin insertion; circular black spot on upper margin of caudal-fin base; black pigment extending from lateral stripe onto pectoral-fin base; no marmorated pattern anterior to dorsal-fin origin; dorsal saddles short, rarely connecting to lateral blotches; 8 (occasionally 7) branched upper caudal-fin rays. 
Distribution. Paracanthocobitis zonalternans is known from the Salween River drainage in Thailand and Myanmar (Fig. 5).


Paracanthocobitis phuketensis (Klausewitz, 1957)
 Phuket Zipper Loach 

 Noemacheilus phuketensis Klausewitz, 1957:195, fig. 1. Type locality: Phuket Island, Thailand. Holotype: SMF 3966. 
Acanthocobitis phuketensis.—Bănărescu & Nalbant, 1964:160. 
Noemacheilus (Acanthocobitis) phuketensis.—Bănărescu & Nalbant, 1968:322.

 Diagnosis. Paracanthocobitis phuketensis is distinguished from all other species of Paracanthocobitis by combination of incomplete lateral line ending near dorsal-fin insertion; 9½–10½ branched dorsal-fin rays; axillary pelvic lobe usually absent, occasionally rudimentary; series of black blotches, sometimes overlain with faint dusky stripe along side of body not obscuring lateral blotches, ending near caudal-fin; circular black spot on upper margin of caudal-fin base; black pigment not extending from black blotches along side of body onto pectoral-fin base; no marmorated pattern anterior to dorsal-fin origin; dorsal saddles longer than interspaces, frequently connecting to lateral blotches; 7–8 branched upper caudal-fin rays. 
Distribution. Paracanthocobitis phuketensis is known from Peninsular Thailand in the Panang Tak drainage and on Phuket Island, south to the Perlis, Padang Sarai, and Ketil drainages of Peninsular Malaysia (Fig. 5).




Paracanthocobitis nigrolineata, new species 
Blacklined Zipper Loach

Diagnosis. Paracanthocobitis nigrolineata is distinguished from all other species of Paracanthocobitis by combination of incomplete lateral line ending near dorsal-fin insertion; 9½–10½ branched dorsal-fin rays; axillary pelvic lobe present; black stripe along side of body, ending near caudal-fin, usually overlying black lateral blotches extending ventrally from lateral stripe; circular black spot on upper margin of caudal-fin base; black pigment extending from lateral stripe onto pectoral-fin base; no marmorated pattern anterior to dorsal-fin origin; black dorsal saddles short, not connecting to lateral blotches; 8 branched upper caudal-fin rays.

Distribution. Paracanthocobitis nigrolineata is known from Irrawaddy and Sittang drainages of Myanmar and the Mae Khlong drainage of Thailand with a large geographic gap in-between (Fig. 5). This gap is likely due to the paucity of sampling in Myanmar.

Etymology. The epithet nigrolineata refers to the black stripe along the side of the body.


Paracanthocobitis triangula, new species 
Wedged Zipper Loach

Diagnosis. Paracanthocobitis triangula is distinguished from all other species of Paracanthocobitis by combination of incomplete lateral line ending near dorsal-fin insertion; 9½–10½ branched dorsal-fin rays; axillary pelvic lobe present; series of black blotches, sometimes overlain with faint dusky stripe along side of body not obscuring lateral blotches, ending just beyond dorsal-fin insertion; small black triangular blotch in ocellus on upper margin of caudal-fin base; black pigment of the midlateral stripe not extending onto pectoral-fin base; no marmorated pattern between dorsal saddles and lateral blotches; dorsal saddles usually extending ventrally just past faint lateral stripe, usually connecting to lateral blotches; 8 branched upper caudal-fin rays.

Distribution. Paracanthocobitis triangula is known from the Brahmaputra (Jamuna) and Meghna drainages of Bangladesh (Fig. 5).
Etymology. The epithet triangula refers to the usual presence of a small black triangular blotch in the ocellus on the upper margin of the caudal peduncle.


Paracanthocobitis marmorata, new species
 Marmorated Zipper Loach

Diagnosis. Paracanthocobitis marmorata is distinguished from all other species of Paracanthocobitis by combination of incomplete lateral line ending just beyond dorsal-fin insertion; 9½–10½ branched dorsal-fin rays; no axillary pelvic lobe; no black stripe along side of body; marmorated pattern of dark lines and blotches between irregularly shaped dorsal saddles dark blotches along side of body; teardrop-shaped black spot on upper margin of caudal-fin base; 8 branched upper caudal-fin rays.

Distribution. Paracanthocobitis marmorata is known from the Barak drainage of Assam, India (Fig. 5).

Etymology. The epithet marmorata refers to the marmorated pattern on the nape and between the dorsal saddles and lateral blotches in lieu of the black stripe along the side of the body typical of other members of the P. zonalternans complex.


 Randal A. Singer, John M. Pfeiffer and Lawrence M. Page. 2017. A Revision of the Paracanthocobitis zonalternans (Cypriniformes: Nemacheilidae) Species Complex with Descriptions of Three New Species. Zootaxa. 4324(1); 85–107.  DOI: 10.11646/zootaxa.4324.1.5

No comments:

Post a Comment